We will continue to study the molecular basis for the regulation of glycogen metabolism in liver. Two lines will be pursued. We will systematically survey liver (and muscle) for relevant and multiple forms of protein phosphatases that might act on the phosphorylated forms of phosphorylase, phosphorylase kinase and glycogen synthase. We will have particular regard to species or protein phosphatase that might act on all three substrates. We are also interested in elucidating the physiological mechanism whereby a protein that inhibits liver phosphorylase phosphatase might be removed, thereby activating the phosphatase. As part of the above study, we will continue our efforts to purify to homogeneity liver phosphorylase kinase. Our second major effort is directed to understanding the structure of glycogen and in particular in providing detailed proof of the glycoprotein nature of liver glycogen. This will involve identifying the nature of the covalent attachment between glycogen and protein, and to sequencing the protein around the point of attachment. We are also interested in learning whether any carbohydrate, other than glucose, intervenes between the glycogen molecule and the protein backbone. BIBLIOGRAPHIC REFERENCES: Purification and Properties of Rabbit-Liver Glycogen Synthase. S.D. Killilea and W.J. Whelan, Biochemistry, 15 (1976) 1349-1356. Evidence for the Coordinate Control of Activity of Liver Glycogen Synthase and Phosphorylase by a Single Protein Phosphatase. S.D. Killilea, H. Brandt, E.Y.C. Lee and W.J. Whelan, J. Biol. Chem. 251 (1976) 2363-2368.